Process for preparing 1-butene cololymer and copolymer thereof

ABSTRACT

A process for preparing isotactic 1-butene copolymers containing up to 30% by mol of units derived from of one or more alpha olefins of formula CH 2 ═CHZ, wherein Z is a C 3 C 20  hydrocarbon group comprising contacting 1-butene and one or more of said alphaolefins under polymerization conditions in the presence of a catalyst system obtainable by contacting: (A) a metallocene compound of formula (I) (1) wherein: M is an atom of a transition metal; p is an integer from 0 to 3; X, same or different, are hydrogen atoms, halogen atoms, or an hydrocarbon group; L is a divalent bridging group; R 1  and R 3  are hydrocarbon groups; R 2  and R 4  are hydrogen atoms or hydrocarbon groups; T 1  and T 2 , equal to or different from each other are a moiety of formula (II), (III) or (IV): wherein: the atom marked with the symbol * is bound the atom marked with the same symbol in formula (I); R 5 , R 6 , R 7 , R 8  and R 9 , equal to or different from each other, are hydrogen or hydrocarbon groups; and (B) an alumoxane or a compound able to form an alkylmetallocene cation.

The present invention relates to a process for preparing copolymers of1-butene and C₅-C₂₂ alpha olefins by using a metallocene-based catalystsystem, and to copolymers obtained by this process.

1-Butene higher alpha-olefin polymers are known as semi-rigid resins.Due to their excellent transparency, surface non tackiness and othertensile properties they can be used, for example, for the production ofpackaging films or sheets or other melt-molded articles. In the artthese copolymers are obtained by using titanium based catalysts. Forexample EP 186 287 describes 1-butene random copolymers obtained byusing titanium tetrachloride supported on magnesium chloride andvinyltrietoxysilane as external donor. EP 352 362 describes 1-butenecopolymers obtained by using titanium based catalyst systems, diisobutylphthalate as internal donor and 1,8 cineole as external donor; moreoverin the comparative examples vinyltrietoxysilane is also used as externaldonor.

When a titanium based catalyst is used the yield of the above process isvery low. Moreover the distribution of the comonomer, as shown by thefraction of polymer soluble in diethyl ether, is not very good and canbe improved.

Recently in WO 02/16450 low isotactic 1-butene copolymers obtained byusing metallocene-based catalyst systems have been described. Thesecopolymers are not endowed with high values of isotacticity.

A new process that permits to obtain an isotactic 1-butene copolymerwith high molecular weight, in high yield and with a good distributionof the comonomer is therefore desirable. An object of the presentinvention is a process for preparing isotactic 1-butene copolymerscontaining up to 30% by mol of one or more alpha olefins of formulaCH₂═CHZ derived units, wherein Z is a C₃-C₂₀ hydrocarbon groupcomprising, contacting 1-butene and one or more of said alpha-olefins,under polymerization conditions, in the presence of a catalyst systemobtainable by contacting:

-   a) at least a metallocene compound of formula (I)    -   wherein    -   M is a transition metal belonging to group 3, 4, 5, 6 or to the        lanthanide or actinide groups in the Periodic Table of the        Elements; preferably M is titanium, zirconium or hafnium;    -   p is an integer from 0 to 3, preferably p is 2, being equal to        the formal oxidation state of the metal M minus 2;    -   X, equal to or different from each other, are hydrogen atoms,        halogen atoms, R, OR, OSO₂CF₃, OCOR, SR, NR₂ or PR₂ groups,        wherein R is a linear or branched, saturated or unsaturated        C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl        or C₇-C₂₀ arylalkyl radical, optionally containing heteroatoms        belonging to groups 13-17 of the Periodic Table of the Elements;        or two X can optionally form a substituted or unsubstituted        butadienyl radical or a OR′O group wherein R′ is a divalent        radical selected from C₁-C₂₀ alkylidene, C₆-C₄₀ arylidene,        C₇-C₄₀ alkylarylidene and C₇-C₄₀ arylalkylidene radicals;        preferably X is a hydrogen atom, a halogen atom or a R group;    -   more preferably X is chlorine or a methyl radical;    -   L is a divalent bridging group selected from C₁-C₂₀ alkylidene,        C₃-C₂₀ cycloalkylidene, C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene,        and C₇-C₂₀ arylalkylidene radicals optionally containing        heteroatoms belonging to groups 13-17 of the Periodic Table of        the Elements, and silylidene radical containing up to 5 silicon        atoms such as SiMe₂, SiPh₂;    -   preferably L is selected from the group consisting of is        Si(CH₃)₂, SiPh₂, SiPhMe, SiMe(SiMe₃), CH₂, (CH₂)₂, (CH₂)₃ and        C(CH₃)₂;    -   R¹ and R³, equal to or different from each other, are linear or        branched, saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀        cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkyl        radicals, optionally containing heteroatoms belonging to groups        13-17 of the Periodic Table of the Elements;    -   R² and R⁴, equal to or different from each other, are hydrogen        atoms or linear or branched, saturated or unsaturated C₁-C₂₀        alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or        C₇-C₂₀ arylalkyl radicals, optionally containing heteroatoms        belonging to groups 13-17 of the Periodic Table of the Elements;        preferably they are hydrogen atoms.    -   T¹ and T², equal to or different from each other are moieties of        formulas (II), (III) or (IV):    -   wherein: the atom marked with the symbol * is bound to the atom        marked with the same symbol in formula (I);    -   R⁵, R⁶, R⁷, R⁸ and R⁹, equal to or different from each other,        are hydrogen atoms, or a linear or branched saturated or        unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₄₀-aryl,        C₇-C₄₀-alkylaryl, C₇-C₄₀-arylalkyl radicals, optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements;    -   R⁶ and R⁷ can also join to form a saturated or unsaturated        condensed 5 to 7 membered ring optionally containing heteroatoms        belonging to groups 13-16 of the Periodic Table of the Elements;        preferably R⁹ is hydrogen or a linear or branched saturated or        unsaturated C₁-C₂₀-alkyl radical;-   b) at least an alumoxane or a compound able to form an    alkylmetallocene cation; and-   c) optionally an organo aluminum compound.

Preferred metallocene compounds of formula (I) belongs to the followingsubclasses:

Subclass (1)

Metallocene compounds belonging to subclass (1) have the followingformula (V):

-   wherein M, L, X and p have been described above;-   R¹⁰, equal to or different from each other, are hydrogen atoms, or    linear or branched saturated or unsaturated C₁-C₁₉-alkyl,    C₃-C₁₉-cycloalkyl, C₆-C₁₉-aryl, C₇-C₁₉-alkylaryl, C₇-C₁₉-arylalkyl    radicals, optionally containing heteroatoms belonging to groups    13-17 of the Periodic Table of the Elements; preferably R¹⁰ is a    hydrogen atom or a C₁-C₁₉-alkyl radical, more preferably R¹⁰ is    hydrogen, methyl or ethyl;-   T³ and T⁴, equal to or different from each other are moieties of    formula (Va), (Vb) or (Vc):-   wherein: the atom marked with the symbol * bonds in formula (V) the    atom marked with the same symbol;-   R⁶, R⁷ and R⁹ have been defined above;-   Preferably R⁶ and R⁷ are hydrogen atoms or linear or branched    saturated or unsaturated C₁-C₂₀-alkyl radicals, or they form a    saturated or unsaturated 5 or 6 membered ring optionally containing    heteroatoms belonging to groups 13-16 of the Periodic Table of the    Elements;-   Preferably R⁹ is a linear or branched saturated or unsaturated    C₁-C₂₀-alkyl radical.    Subclass (2)

Metallocene compounds belonging to subclass (2) have the followingformula (VD):

-   wherein R¹⁰, M, L, X and p have been described above;-   T⁵ and T⁶, equal to or different from each other are moieties of    formula (VIa), (VIb) or (VIc):-   wherein: the atom marked with the symbol * is bound to the atom    marked with the same symbol in formula (VI);-   R⁶, R⁷ and R⁹, have been defined above;-   Preferably R⁶ and R⁷ are hydrogen atoms or linear or branched    saturated or unsaturated C₁-C₂₀-alkyl radicals; or they form a    saturated or unsaturaded 5 or 6 membered ring optionally containing    heteroatoms heteroatoms belonging to groups 13-16 of the Periodic    Table of the Elements;-   Preferably R⁹ is a hydrogen atom or a linear or branched saturated    or unsaturated C₁-C₂₀-alkyl radical;-   R¹¹, R¹², R¹³, R¹⁴, and R¹⁵, equal to or different from each other,    are hydrogen atoms or linear or branched saturated or unsaturated    C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl,    C₇-C₂₀-arylalkyl radicals, optionally containing heteroatoms    belonging to groups 13-17 of the Periodic Table of the Elements, or    two adjacent groups can form together a saturated or unsaturated    condensed 5 or 6 membered ring optionally containing heteroatoms    belonging to groups 13-16 of the Periodic Table of the Elements;    preferably R¹¹ is a C₁-C₂₀-alkyl radical; more preferably R¹¹ is a    methyl radical; preferably R¹⁴ is a hydrogen atom or a C₁-C₂₀-alkyl    radical; more preferably R¹⁴ is a methyl radical; preferably R¹²,    R¹³ and R¹⁵ are hydrogen atoms.

Metallocene compounds belonging to formulas (I), (V) and (VI) are wellknown in the art; in particular they are described in U.S. Pat. No.5,145,819, EP-A-0 485 823, WO 98/22486, WO 01/44318, U.S. Pat. No.5,786,432 and EP02080120.5.

Preferably the metallocene compounds of formula (I) are in the racemic(rac) form.

Examples of alumoxanes suitable for use according to the presentinvention are methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO),tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO),tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) andtetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).

Particularly interesting cocatalysts are those described in WO 99/21899and in WO01/21674 in which the alkyl and aryl groups have specificbranched patterns.

Non-limiting examples of aluminium compounds according to WO 99/21899and WO01/21674 are:

-   tris(2,3,3-trimethyl-butyl)aluminium,    tris(2,3-dimethyl-hexyl)aluminium, tris(2,3-dimethylbutyl)aluminium,    tris(2,3-dimethyl-pentyl)aluminium,    tris(2,3-dimethyl-heptyl)aluminium,    tris(2-methyl-3-ethyl-pentyl)aluminium,    tris(2-methyl-3-ethyl-hexyl)aluminium,    tris(2-methyl-3-ethyl-heptyl)aluminium,    tris(2-methyl-3-propyl-hexyl)aluminium,    tris(2-ethyl-3-methyl-butyl)aluminium,    tris(2-ethyl-3-methyl-pentyl)aluminium,    tris(2,3-diethyl-pentyl)aluminium,    tris(2-propyl-3-methyl-butyl)aluminium,    tris(2-isopropyl-3-methyl-butyl)aluminium,    tris(2-isobutyl-3-methyl-pentyl)aluminium,    tris(2,3,3-trimethyl-pentyl)aluminium,    tris(2,3,3-trimethyl-hexyl)aluminium,    tris(2-ethyl-3,3-dimethylbutyl)aluminium,    tris(2-ethyl-3,3-dimethyl-pentyl)aluminium,    tris(2-isopropyl-3,3-dimethylbutyl)aluminium,    tris(2-trimethylsilyl-propyl)aluminium,    tris(2-methyl-3-phenyl-butyl)aluminium,    tris(2-ethyl-3-phenyl-butyl)aluminium,    tris(2,3-dimethyl-3-phenyl-butyl)aluminium,    tris(2-phenyl-propyl)aluminium,    tris[2-(4-fluoro-phenyl)-propyl]aluminium,    tris[2-(4-chloro-phenyl)-propyl]aluminium,    tris[2-(3-isopropyl-phenyl)-propyl]aluminium,    tris(2-phenyl-butyl)aluminium,    tris(3-methyl-2-phenyl-butyl)aluminium,    tris(2-phenyl-pentyl)aluminium,    tris[2-(pentafluorophenyl)-propyl]aluminium,    tris[2,2-diphenyl-ethyl]aluminium and    tris[2-phenyl-2-methyl-propyl]aluminium, as well as the    corresponding compounds wherein one of the hydrocarbyl groups is    replaced with a hydrogen atom, and those wherein one or two of the    hydrocarbyl groups are replaced with an isobutyl group.

Amongst the above aluminium compounds, trimethylaluminium (TMA),triisobutylaluminium (TIBAL), tris(2,4,4-trimethyl-pentyl)aluminium(TIOA), tris(2,3-dimethylbutyl)aluminium (TDMBA) andtris(2,3,3-trimethylbutyl)aluminium (TTMBA) are preferred.

Non-limiting examples of compounds able to form an alkylmetallocenecation are compounds of formula D⁺E⁻, wherein D⁺ is a Brønsted acid,able to donate a proton and to react irreversibly with a substituent Xof the metallocene of formula (I) and E⁻ is a compatible anion, which isable to stabilize the active catalytic species originating from thereaction of the two compounds, and which is sufficiently labile to beable to be removed by an olefinic monomer. Preferably, the anion E⁻comprises of one or more boron atoms. More preferably, the anion E⁻ isan anion of the formula BAr₄ ⁽⁻⁾, wherein the substituents Ar which canbe identical or different are aryl radicals such as phenyl,pentafluorophenyl or bis(trifluoromethyl)phenyl.Tetrakis-pentafluorophenyl borate is particularly preferred examples ofthese compounds are described in WO 91/02012. Moreover, compounds of theformula BAr₃ can conveniently be used. Compounds of this type aredescribed, for example, in the published International patentapplication WO 92/00333. Other examples of compounds able to form analkylmetallocene cation are compounds of formula BAr₃P wherein P is asubstituted or unsubstituted pyrrol radicals. These compounds aredescribed in WO01/62764. Other examples of cocatalyst can be found in EP775707 and DE 19917985. Compounds containing boron atoms can beconveniently supported according to the description of DE-A-19962814 andDE-A-19962910. All these compounds containing boron atoms can be used ina molar ratio between boron and the metal of the metallocene comprisedbetween about 1:1 and about 10:1; preferably 1:1 and 2.1; morepreferably about 1:1.

Non limiting examples of compounds of formula D⁺E⁻ are:

-   Triethylammoniumtetra(phenyl)borate,-   Tributylammoniumtetra(phenyl)borate,-   Trimethylammoniumtetra(tolyl)borate,-   Tributylammoniumtetra(tolyl)borate,-   Tributylammoniumtetra(pentafluorophenyl)borate,-   Tributylammoniumtetra(pentafluorophenyl)aluminate,-   Tripropylammoniumtetra(dimethylphenyl)borate,-   Tributylammoniumtetra(trifluoromethylphenyl)borate,-   Tributylammoniumtetra(4-fluorophenyl)borate,-   N,N-Dimethylbenzylammonium-tetrakispentafluorophenylborate,-   N,N-Dimethylhexylamonium-tetrakispentafluorophenylborate,-   N,N-Dimethylaniliniumtetra(phenyl)borate,-   N,N-Diethylaniliniumtetra(phenyl)borate,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)aluminate,-   N,N-Dimethylbenzylammonium-tetrakispentafluorophenylborate,-   N,N-Dimethylhexylamonium-tetrakispentafluorophenylborate,-   Di(propyl)amnoniumtetrakis(pentafluorophenyl)borate,-   Di(cyclohexyl)ammoniumtetrakis(pentafluorophenyl)borate,-   Triphenylphosphoniumtetrakis(phenyl)borate,-   Triethylphosphoniumtetrakis(phenyl)borate,-   Diphenylphosphoniumtetrakis(phenyl)borate,-   Tri(methylphenyl)phosphoniumtetrakis(phenyl)borate,-   Tri(dimethylphenyl)phosphoniumtetrakis(phenyl)borate,-   Triphenylcarbeniumtetrakis(pentafluorophenyl)borate,-   Triphenylcarbeniumtetrakis(pentafluorophenyl)aluminate,-   Triphenylcarbeniumtetrakis(phenyl)aluminate,-   Ferroceniumtetrakis(pentafluorophenyl)borate,-   Ferroceniumtetrakis(pentafluorophenyl)aluminate.-   Triphenylcarbeniumtetrakis(pentafluorophenyl)borate,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate.

Organic aluminum compounds used as compound c) are those of formulaH_(j)AlU_(3-j) or H_(j)Al₂U_(6-j) described above.

The polymerization process of the present invention can be carried outin liquid phase. The polymerization medium can be 1-butene optionally inthe presence of an inert hydrocarbon solvent. Said hydrocarbon solventcan be either aromatic (such as toluene) or aliphatic (such as propane,hexane, heptane, isobutane, cyclohexane and 2,2,4-trimethylpentane).Otherwise the polymerization process of the present invention can becarried out in a gas phase. Preferably the polymerization is carried outby using liquid 1-butene as the polymerization medium (bulkpolymerization).

The catalyst system of the present invention can also be supported on aninert carrier. This is achieved by depositing the metallocene compounda) or the product of the reaction thereof with the component b), or thecomponent b) and then the metallocene compound a) on an inert supportsuch as, for example, silica, alumina, Al—Si, Al—Mg mixed oxides,magnesium halides, styrene/divinylbenzene copolymers, polyethylene orpolypropylene. The supportation process is carried out in an inertsolvent, such as hydrocarbon selected from toluene, hexane, pentane andpropane and at a temperature ranging from 0° C. to 100° C., more from30° C. to 60° C.

A particularly suitable process for supporting the catalyst system isdescribed in WO01/44319, wherein the process comprises the steps of:

-   (a) preparing a catalyst solution comprising a soluble catalyst    component;-   (b) introducing into a contacting vessel:-   (i) a porous support material in particle form, and-   (ii) a volume of the catalyst solution not greater than the total    pore volume of the porous support material introduced;-   (c) discharging the material resulting from step (b) from the    contacting vessel and suspending it in an inert gas flow, under such    conditions that the solvent evaporates; and-   (d) reintroducing at least part of the material resulting from    step (c) into the contacting vessel together with another volume of    the catalyst solution not greater than the total pore volume of the    reintroduced material.

A suitable class of supports comprises porous organic supportsfunctionalized with groups having active hydrogen atoms. Particularlysuitable are those in which the organic support is a partiallycrosslinked styrene polymer. Supports of this type are described in EP633 272.

Another class of inert supports particularly suitable for use accordingto the invention is that of polyolefin porous prepolymers, particularlypolyethylene.

A further suitable class of inert supports for use according to theinvention is that of porous magnesium halides, such as those describedin WO 95/32995.

The polymerization temperature preferably ranges from 0° C. to 250° C.;preferably comprised between 20° C. and 150° C. and, more particularlybetween 40° C. and 90° C.

The molecular weight distribution of the polymer obtained with theprocess of the present invention can be varied by using mixtures ofdifferent metallocene compounds or mixtures of the metallocene compoundof formula (I) and a Ziegler-Natta catalyst or by carrying out thepolymerization in several stages at different polymerizationtemperatures and/or different concentrations of the molecular weightregulators and/or different monomer concentration.

The polymerization yield depends on the purity of the transition metalorganometallic catalyst compound a) in the catalyst, therefore, saidcompound can be used as such or can be subjected to purificationtreatments before use.

With the process according to the present invention it is possible toprepare isotactic 1-butene copolymers containing up to 30% by mol ofunits derived from one or more alpha-olefins of formula CH₂═CHZ, whereinZ is a C₃-C₂₀ hydrocarbon group. Examples of alpha-olefins are1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene,4,6-dimethyl-1-heptene, 1-decene, 1-dodecene, 1-tetradecene,1-hexadecene, 1-octadecene and 1-eicosene. Preferred comonomersare-1-pentene, 1-hexene and 1-octene; preferably the comonomer is1-hexene.

Preferably the content of said alpha olefins derived units ranges from2% to 20% by mol, more preferably from 3% to 17% by mol.

The 1-butene copolymers obtained with the process of the presentinvention are highly isotactic, and show a high molecular weight, thatrenders them useful for an industrial use. Moreover the 1-butenecopolymers object of the present invention are characterised by highcontent of diethylether solubles that is an indication of good comonomerdistribution. Furthermore 4,1 regioinsertions of 1-butene are present inthe polymer chain. The presence of 4,1 regioerrors along the polymerchain enhances the effect of the introduction of the comonomer, thuslowering the degree of crystallinity. The presence of 4,1 insertions of1-butene may be evaluated by ¹³C-NMR. Assignments of 4,1 insertion canbe made according to Busico (V. Busico, R. Cipullo, A. Borriello,Macromol. Rapid. Commun. 1995, 16, 269-274)

Thus, a further object of the present invention is an isotactic 1-butenecopolymer containing up to 30% by mol of units derived from one or morealpha-olefins of formula CH₂═CHZ, wherein Z is a C₃-C₂₀ hydrocarbongroup having the following features:

-   -   isotactic pentads (mmmm)>90%; preferably >95%; more        preferably >98%; and    -   the percentage of soluble fraction in diethylether (% SD) and        the molar content of said alpha-olefin (% O) in the polymer        chain meet the following relation:        % SD>2.8% O+8.

Preferably the relation is % SD>2.8% O+10; more preferably the relationis % SD>2.8% O+15; a further preferred relation is % SD>2.8% O+20.

When the content of alpha olefins is comprised between 10% and 30% thecopolymers obtained according to the present invention are characterizedby the following features:

-   -   isotactic pentads (mmmm)>90%; preferably >95%; more        preferably >98%; and    -   percentage of soluble fraction in diethylether >92%; preferably        >94%.

Preferably the content of alpha-olefin derived units is comprisedbetween 11% and 25%. When the content of alpha olefin is comprisedbetween 5% and 12% the copolymers obtained according to the presentinvention are characterized by the following features:

-   -   isotactic pentads (mmmm)>90%; preferably >95%; more        preferably >98%; and    -   percentage of soluble fraction in diethylether >41%; preferably        >46%.

The 1-butene copolymers obtained according to the present invention arefurther characterized by the presence of 4,1 insertions in the polymerchain. Thus a further object of the present invention is an isotactic1-butene copolymer containing up to 30% by mol of units derived from oneor more alpha-olefins of formula CH₂═CHZ, wherein Z is a C₃-C₂₀hydrocarbon group having the following features:

-   -   isotactic pentads (mmmm)>90%; preferably >95%; more        preferably >98%; and    -   presence of 4,1 insertions in the polymer chain.

Preferably the 4,1 insertions are higher than 0.02%, more preferablythey are comprised between 0.05% and 0.4%.

The 1-butene copolymers object of the present invention are furtherendowed with a molecular weight distribution Mw/Mn<4; preferablyMw/Mn<3; more preferably Mw/Mn<2.5.

The molecular weight (I.V.) measured in decahydronaphtalene is higherthan 1 dl/g, preferably higher than 1.25 dl/g.

The 1-butene copolymers of the present invention can be advantageouslyused as components in blend with other polyolefins such as isotactic orsyndiotactic polypropylene homo and copolymer, 1-butene homopolymer, andethylene homo and copolymer. The following examples are given toillustrate and not to limit the invention.

EXPERIMENTAL SECTION

The intrinsic viscosity (I.V.) was measured in decahydronaphthalene(DHN) at 135°.

The melting points of the polymers (T_(m)) were measured by using aPerkin-Elmer DSC-7 calorimeter equipped with Pyris 1 software. Theinstrument was calibrated at indium and zinc melting points withparticular attention in determining the baseline with required accuracy.

Melting points were measured according to the following method aweighted sample (4-8 mg) obtained from the polymerization was sealedinto an aluminum pan, the sample was then subjected to the followingthermal treatment:

-   i) first heating run from room temperature to 180° C. with a    scanning rate of 10° C./min;-   ii) annealing run at 180° C. for 5 minutes;-   iii) crystallization run from 180° C. to 0° C., at 10° C./min in    order to crystallize the sample under controlled conditions;-   iv) second heating run from room temperature to 180° C.

In this second heating run, the maximum peak temperature was taken asthe melting temperature (T_(m)).

The molecular weight distribution was determined on a WATERS 150 C usingthe following chromatographic conditions: Columns: 3× SHODEX AT 806 MS;1× SHODEX UT 807; 1× SHODEX AT-G; Solvent: 1,2,4 trichlorobenzene(+0.025% 2,6-Di- tert.Butyl-4-Methyl-Phenol); Flow rate: 0.6-1 ml/min;Temperature: 135° C.; Detector: INFRARED AT λ ≅ 3.5 μm; Calibration:Universal Calibration with PS-Standards.

¹³C-NMR spectra were acquired on a DPX-400 spectrometer operating at100.61 MHz in the Fourier transform mode at 120° C. The peak of the 2B₂carbon (nomenclature according to Carman, C. J.; Harrington, R. A.;Wilkes, C. E. Macromolecules 1977, 10, 535) was used as internalreference at 27.73. The samples were dissolved in1,1,2,2-tetrachloroethane-d2 at 120° C. with a 8% wt/v concentration.Each spectrum was acquired with a 90° pulse, 15 seconds of delay betweenpulses and CPD (waltz16) to remove 1H-13C coupling. About 600 transientswere stored in 32K data points using a spectral window of 6000 Hz.Assignments of 4,1 insertion were made according to Busico (V. Busico,R. Cipullo, A. Borriello, Macromol. Rapid. Commun. 1995, 16, 269-274).

Diethyl Ether Solubility

About 1 gram of polymer was transferred to a glass flask equipped with amagnetic stirrer and 250 cc of diethyl ether was added. The solution wasstirred for 24 hours at room temperature under N₂ to dissolve thesoluble fraction of the polymer. After the dissolution the liquid wasfiltered with a paper filter, to separate the remaining solid from thesolution, and was transferred to a glass flask, previously weighted. Thesolvent was removed under vacuum and the polymer obtained was dried in awarm vacuum oven for 1 day to eliminate all solvent traces. The flaskwas weighted and the quantity of soluble polymer was determined.

Preparation of Catalyst Components

Rac dimethylsilylbis(2-methyl-indenyl) zirconium dichloride (A-1) wasprepared according to U.S. Pat. No. 5,145,819. Racdimethylsilandiylbis-6-[2,5-dimethyl-3-(2′,5′-dimethylphenyl)cyclopentadienyl-[1,2-b]-thiophene]zirconiumdichloride (A-2) is prepared according to WO01/44318.

The cocatalyst methylalumoxane (MAO) was a commercial product which wasused as received (Witco AG, 10% wt/vol toluene solution, 1.7 M in Al).

Catalyst Solution Preparation Procedure

3 mg of the metallocene compounds indicated in table 1 were added to atoluene solution of methylalumoxane (MAO 10% weight/volume) to obtainthe desired MAO/Zr ratio. If necessary, additional toluene was added toobtain a final volume of 5-10 ml, easy to be fed into the autoclave. Thecatalyst solution was inserted into the steel cylinder and then fed intothe autoclave as reported above.

Polymerization Examples 1-8

A 4.25 litres steel autoclave, equipped with magnetically stirred anchor(usual stirring rate 550 rpm) and with a Flow Record & Control systems(FRC) having maximum flow rate of 9000 gr/hour for 1-butene, was purgedwith hot nitrogen (1.5 barg N₂, 70° C., 1 hour). Then, stirring wasstarted and 1-butene and 1-hexene were fed into the reactor (amountsindicated in table 1). Subsequently, the reactor inner temperature wasraised from 30° C. to the polymerisation temperature of 70° C. Whenpressure and temperature were constant, the catalytic solution was fedinto the reactor with a nitrogen overpressure and the polymerization wascarried out for the time indicated in table 1.

Then the stirring was interrupted; the pressure into the autoclave wasraised to 20 bar-g with nitrogen. The bottom discharge valve was openedand the comonomer/copolymer mixture was discharged into the heated steeltank containing water at 70° C. The tank heating was switched off and aflux of 0.5 bar-g nitrogen was fed. After 1 hour cooling at roomtemperature the steel tank was opened and the wet polymer collected. Thewet polymer was dried in a oven under nitrogen at 70° C. Thepolymerization conditions and the characterization data of the obtainedpolymers are reported in Table 1.

Characterization of Copolymers

Samples of polymer obtained from examples 1 and 2 and a sample of an1-butene/ethyle copolymer having an ethylene content of 2.3% by wtprepared according to example 11 of PCT/EP02/06574 (sample A used forcomparison) were mixed in a Brabender® chamber with 1%2,6-di-t-butyl-4-methyl phenol (BHT) at 180° C. and then transformed in1.9 and 4 mm thick plaques through compression molding at 200° C. withan cooling of 30′/min.

The 1.9 mm thick plaques were submitted to tensile test (according toASTM D 638 method), while the 4.0 mm thick plaques were submitted to theflexural modulus determination according to ISO 178 method.

tensile modulus was calculated according the following equation:tensile modulus=(1−3% chord)=(T3%−T1%)/0.02

-   wherein T3%=stress at 3% deformation; and-   wherein T1%=stress at 1% deformation.

The results are reported in table 2 TABLE 1 liquid phase composition C₆Al/ 1-Butene, 1-Hexene, time Activity % mol Ex. Met Zr g g minkg/g_(met)*h (NMR) 1 A-2 1000 1350 69 30 135.3 3.22 2 A-2 1000 1290 14015 296.0 5.94 3 A-2 1000 1216 226 60 111.3 11.2 4 A-2 1000 1140 314 6085.3 15.8 5 A-1 675 1350 69 60 139 3.6 6 A-1 675 1290 140 60 202 7.28 7A-1 500 1216 226 60 70 9.34 8 A-1 675 1140 314 60 32 16.7 4.1 I.V.insertions (DHN, T_(m)(II) ΔH_(f) % SD mmmm Ex % dL/g) ° C. J/gM_(w)/M_(n) % % 1 0.22 1.56 94.0 27.3 2.1 n.a. >95 2 0.30 1.30 80.4 14.62.4 76.9 >95 3 n.a. 1.48 59.6 10.9 2.2 94.1 >95 4 0.26 1.44 54.9 ^(a))n.a. 2.1 n.a. >95 5 0.25 1.50 82.2 21 2.3 n.a. n.a. 6 0.20 1.34 67.117.8. 2.1 n.a. n.a. 7 0.29 1.49 60.1 15.2 2.3 n.a. n.a. 8 0.25 1.43 48.7^(a)) n.a. 2.2 n.a. n.a.n.a. = not available^(a)) after annealing at room temperature for 30 days

TABLE 2 Example A 1 2 Ethylene content % wt (IR) 2.3 — — Hexene content% wt (NMR) — 4.75 8.65 % mol (NMR) — 3.22 5.94 Melt flow rate E g/10′5.0 3.9  4.5  T_(m) Form II ° C. 75 93   80 ^(a)  ΔH_(f) Form II J/gn.a. 32 ^(a)  26 ^(a)  Tensile modulus MPa 103 106   85   (1-3% chord)Tensile strength at yield MPa 6.6 6.6  5.3  Tensile strength at breakMPa 37.1 36.7  33.2  Elongation at break % 434 366   444  n.a. = not available^(a) after annealing at room temperature for 30 days

A comparison between the butene-ethylene (2.3% wt C₂, IR) copolymer ofthe prior art and the butene-hexene copolymer according to the presentinvention (4.75% wt C₆, ¹³C NMR) points out the higher meltingtemperature and melting enthalpy of the latter, all the other propertiesbeing the same.

A comparison between the same butene-ethylene (2.3% wt C₂, IR) copolymerof the prior art and a more modified butene-hexene copolymer (8.65% wtC₆, ¹³C NMR) according to the present invention points out the highermelting temperature and flexibility of the latter, all the otherproperties being similar. In table 2 the superiority of thebutene-hexene copolymers of the present invention with respect to thebutene-ethylene copolymer of the prior art is shown by a better thermalresistance and a higher flexibility.

1. A process for preparing isotactic 1-butene copolymers having acontent up to 30% by mol of units derived from at least one alpha olefinof formula CH₂═CHZ, wherein Z is a C₃-C₂₀ hydrocarbon group, the processcomprising contacting 1-butene and the at least one alpha olefin underpolymerization conditions, in the presence of a catalyst system obtainedby contacting: a) at least a metallocene compound of formula (I):

wherein M is a transition metal belonging to group 3, 4, 5, 6 or to thelanthanide or actinide groups in the Periodic Table of the Elements; pis an integer from 0 to 3, being equal to the formal oxidation state ofthe metal M minus 2; X, equal to or different from each other, arehydrogen atoms, halogen atoms, or R, OR, OSO₂CF₃, OCOR, SR, NR₂ or PR₂groups, wherein R is a linear or branched, saturated or unsaturatedC₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀arylalkyl radical, optionally containing heteroatoms belonging to groups13-17 of the Periodic Table of the Elements; or two X can optionallyform a substituted or unsubstituted butadienyl radical or a OR′O groupwherein R′ is a divalent radical selected from C₁-C₂₀ alkylidene, C₆-C₄₀arylidene, C₇-C₄₀ alkylarylidene and C₇-C₄₀ arylalkylidene radicals; Lis a divalent bridging group selected from C₁-C₂₀ alkylidene, C₃-C₂₀cycloalkylidene, C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene, and C₇-C₂₀arylalkylidene radicals optionally containing heteroatoms belonging togroups 13-17 of the Periodic Table of the Elements, and silylideneradical containing up to 5 silicon atoms; R¹ and R³, equal to ordifferent from each other, are linear or branched, saturated orunsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl or C₇-C₂₀ arylalkyl radicals, optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; R² and R⁴, equal to or different from each other, are hydrogenatoms or linear or branched, saturated or unsaturated C₁-C₂₀ alkyl,C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkylradicals, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; T¹ and T², equal to or differentfrom each other are a moiety of formula (II), (III) or (IV):

wherein the atom marked with the * is bound to the atom marked with thesame symbol bonds in formula (I); R⁵, R⁶, R⁷, R⁸ and R⁹, equal to ordifferent from each other, are hydrogen atoms, or a linear or branchedsaturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₄₀-aryl,C₇-C₄₀-alkylaryl, C₇-C₄₀-arylalkyl radicals, optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; R⁶ and R⁷ can also join to form a saturated or unsaturatedcondensed 5 to 7 membered ring optionally containing heteroatomsbelonging to groups 13-16 of the Periodic Table of the Elements; and b)at least an alumoxane or a compound that forms an alkylmetallocenecation.
 2. The process according to claim 1 wherein the catalyst systemfurther comprises an organo aluminum compound.
 3. The process accordingto claim 1 wherein in the compound of formula (I), M is titanium,zirconium or hafnium; X is a hydrogen atom, a halogen atom or a R group;L is selected from the group consisting of Si(CH₃)₂, SiPh₂, SiPhMe,SiMe(SiMe₃), CH₂, (CH₂)₂, (CH₂)₃ and C(CH₃)₂ and R⁹ is a hydrogen atomor a linear or branched saturated or unsaturated C₁-C₂₀-alkyl radical.4. The process according to claim 1 wherein the metallocene compound hasformula (V):

wherein R¹⁰, equal to or different from each other, are hydrogen atoms,or linear or branched saturated or unsaturated C₁-C₁₉-alkyl,C₃-C₁₉-cycloalkyl, C₆-C₁₉-aryl, C₇-C₁₉-alkylaryl, C₇-C₁₉-arylalkylradicals, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; T³ and T⁴, equal to or differentfrom each other are moieties of formula (Va), (Vb) or (Vc):

wherein the atom marked with the symbol * is bound to the atom markedwith the same symbol in formula (V).
 5. The process according to claim 4wherein in the compound of formula (V), R¹⁰ is a hydrogen atom or aC₁-C₁₉-alkyl radical; R⁶, R⁷ are hydrogen atoms or linear or branchedsaturated or unsaturated C₁-C₂₀-alkyl radicals, or they form a saturatedor unsaturaded 5 or 6 membered ring optionally containing heteroatomsbelonging to groups 13-16 of the Periodic Table of the Elements; and R⁹is a linear or branched saturated or unsaturated C₁-C₂₀-alkyl radical.6. The process according to claim 1 wherein the metallocene compound hasformula (VI):

wherein R¹⁰, equal to or different from each other, are hydrogen atoms,or linear or branched saturated or unsaturated C₁-C₁₉-alkyl,C₃-C₁₉-cycloalkyl, C₆-C₁₉-aryl, C₇-C₁₉-alkylaryl, C₇-C₁₉-arylalkylradicals, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; T⁵ and T⁶, equal to or differentfrom each other are a moiety of formula (VIa), (VIb) or (VIc):

wherein the atom marked with the symbol * is bound to the atom markedwith the same symbol in formula (VI); R¹¹, R¹², R¹³, R¹⁴, and R¹⁵, equalto or different from each other, are hydrogen atoms or linear orbranched saturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl,C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl, C₇-C₂₀-arylalkyl radicals, optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements, or two adjacent groups form together a saturated orunsaturated condensed 5 or 6 membered ring optionally containingheteroatoms belonging to groups 13-16 of the Periodic Table of theElements.
 7. The process according to claim 6 wherein R⁶ and R⁷ arehydrogen atoms or linear or branched saturated or unsaturatedC₁-C₂₀-alkyl radicals; or they form a saturated or unsaturaded 5 or 6membered ring optionally containing heteroatoms belonging to groups13-16 of the Periodic Table of the Elements; R⁹ is a hydrogen atom or alinear or branched saturated or unsaturated C₁-C₂₀-alkyl radical; R¹¹ isa C₁-C₂₀-alkyl radical; R¹⁴ is a hydrogen atom or a C₁-C₂₀-alkylradical; and R¹², R¹³ and R¹⁵ are hydrogen atoms.
 8. The processaccording to claim 1 wherein the alpha-olefin is selected from1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene,4,6-dimethyl-1-heptene, 1-decene, 1-dodecene, 1-tetradecene,1-hexadecene, 1-octadecene and 1-eicosene.
 9. The process according toclaim 8 wherein the alpha-olefin is selected from 1-pentene, 1-hexeneand 1-octene.
 10. The process according to claim 1 wherein the contentof the at least one alpha olefin derived units in the copolymer is from2% to 20% by mol.
 11. An isotactic 1-butene copolymer having a contentup to 30% by mol of at least one alpha-olefin of formula CH₂═CHZ derivedunits, wherein Z is a C₃-C₂₀ hydrocarbon group having the followingfeatures: (i) isotactic pentads (mmmm)>90%; and (ii) a percentage ofsoluble fraction in diethylether (% SD) and a molar content of saidalpha olefins (% O) in the polymer chain meeting the following relation:% SD>2.8% O+8.
 12. The isotactic 1-butene copolymer according to claim11 wherein the percentage of soluble fraction content in diethylether (%SD) and the molar content of said alpha olefins (% O) in the polymerchain meet the following relation:% SD>2.8% O+10.
 13. The isotactic 1-butene copolymer according to claim11 wherein the content of alpha-olefin derived units are comprisedbetween 10% and 30% by mol and the percentage of soluble fraction indiethylether >92%.
 14. The isotactic 1-butene copolymer according toclaim 11 wherein the content of alpha-olefin derived units are comprisedbetween 5% and 12% by mol and the percentage of soluble fraction indiethylether >41%.
 15. An isotactic 1-butene copolymer having a contentup to 30% by mol of units derived from at least one alpha olefin offormula CH₂═CHZ, wherein Z is a C₃-C₂₀ hydrocarbon group having thefollowing features: (i) isotactic pentads (mmmm)>90%; and (ii) presenceof 4,1 insertions in the polymer chain.
 16. An isotactic 1-butenecopolymer having a content up to 30% by mol of at least one alpha-olefinof formula CH₂═CHZ derived units, wherein Z is a C₃-C₂₀ hydrocarbongroup having the following features: (i) isotactic pentads (mmmm)>90%;and (ii) a percentage of soluble fraction in diethylether (% SD) and amolar content of said alpha olefins (% O) in the polymer chain meetingthe following relation:% SD>2.8% O+8, produced by a process comprising contacting 1-butene andthe at least one alpha olefin under polymerization conditions, in thepresence of a catalyst system obtained by contacting: a) at least ametallocene compound of formula (I):

wherein M is a transition metal belonging to group 3, 4, 5, 6 or to thelanthanide or actinide groups in the Periodic Table of the Elements; pis an integer from 0 to 3, being equal to the formal oxidation state ofthe metal M minus 2; X, equal to or different from each other, arehydrogen atoms, halogen atoms, or R, OR, OSO₂CF₃, OCOR, SR, NR₂ or PR₂groups, wherein R is a linear or branched, saturated or unsaturatedC₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀arylalkyl radical, optionally containing heteroatoms belonging to groups13-17 of the Periodic Table of the Elements; or two X can optionallyform a substituted or unsubstituted butadienyl radical or a OR′O groupwherein R′ is a divalent radical selected from C₁-C₂₀ alkylidene, C₆-C₄₀arylidene, C₇-C₄₀ alkylarylidene and C₇-C₄₀ arylalkylidene radicals; Lis a divalent bridging group selected from C₁-C₂₀ alkylidene, C₃-C₂₀cycloalkylidene, C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene, and C₇-C₂₀arylalkylidene radicals optionally containing heteroatoms belonging togroups 13-17 of the Periodic Table of the Elements, and silylideneradical containing up to 5 silicon atoms; R¹ and R³, equal to ordifferent from each other, are linear or branched, saturated orunsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl or C₇-C₂₀ arylalkyl radicals, optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; R² and R⁴, equal to or different from each other, are hydrogenatoms or linear or branched, saturated or unsaturated C₁-C₂₀ alkyl,C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkylradicals, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; T¹ and T², equal to or differentfrom each other are a moiety of formula (II), (III) or (IV):

wherein the atom marked with the * is bound to the atom marked with thesame symbol bonds in formula (I); R⁵, R⁶, R⁷, R⁸ and R⁹, equal to ordifferent from each other, are hydrogen atoms, or a linear or branchedsaturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₄₀-aryl,C₇-C₄₀-alkylaryl, C₇-C₄₀-arylalkyl radicals, optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; R⁶ and R⁷ can also join to form a saturated or unsaturatedcondensed 5 to 7 membered ring optionally containing heteroatomsbelonging to groups 13-16 of the Periodic Table of the Elements; and b)at least an alumoxane or a compound that forms an alkylmetallocenecation.
 17. An isotactic 1-butene copolymer having a content up to 30%by mol of units derived from at least one alpha olefin of formulaCH₂═CHZ, wherein Z is a C₃-C₂₀ hydrocarbon group having the followingfeatures: (i) isotactic pentads (mmmm)>90%; and (ii) presence of 4,1insertions in the polymer chain, produced by a process comprisingcontacting 1-butene and the at least one alpha olefin underpolymerization conditions, in the presence of a catalyst system obtainedby contacting: a) at least a metallocene compound of formula (I):

wherein M is a transition metal belonging to group 3, 4, 5, 6 or to thelanthanide or actinide groups in the Periodic Table of the Elements; pis an integer from 0 to 3, being equal to the formal oxidation state ofthe metal M minus 2; X, equal to or different from each other, arehydrogen atoms, halogen atoms, or R, OR, OSO₂CF₃, OCOR, SR, NR₂ or PR₂groups, wherein R is a linear or branched, saturated or unsaturatedC₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀arylalkyl radical, optionally containing heteroatoms belonging to groups13-17 of the Periodic Table of the Elements; or two X can optionallyform a substituted or unsubstituted butadienyl radical or a OR′O groupwherein R′ is a divalent radical selected from C₁-C₂₀ alkylidene, C₆-C₄₀arylidene, C₇-C₄₀ alkylarylidene and C₇-C₄₀ arylalkylidene radicals; Lis a divalent bridging group selected from C₁-C₂₀ alkylidene, C₃-C₂₀cycloalkylidene, C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene, and C₇-C₂₀arylalkylidene radicals optionally containing heteroatoms belonging togroups 13-17 of the Periodic Table of the Elements, and silylideneradical containing up to 5 silicon atoms; R¹ and R³, equal to ordifferent from each other, are linear or branched, saturated orunsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl or C₇-C₂₀ arylalkyl radicals, optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; R² and R⁴, equal to or different from each other, are hydrogenatoms or linear or branched, saturated or unsaturated C₁-C₂₀ alkyl,C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkylradicals, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; T¹ and T², equal to or differentfrom each other are a moiety of formula (II), (III) or (IV):

wherein the atom marked with the * is bound to the atom marked with thesame symbol bonds in formula (1); R⁵, R⁶, R⁷, R⁸ and R⁹, equal to ordifferent from each other, are hydrogen atoms, or a linear or branchedsaturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₄₀-aryl,C₇-C₄₀-alkylaryl, C₇-C₄₀-arylalkyl radicals, optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; R⁶ and R⁷ can also join to form a saturated or unsaturatedcondensed 5 to 7 membered ring optionally containing heteroatomsbelonging to groups 13-16 of the Periodic Table of the Elements; and b)at least an alumoxane or a compound that forms an alkylmetallocenecation.